CMOS (Complementary Metal-Oxide Semiconductor) image sensors may exemplify solid-state imaging devices installed in digital video cameras, digital still cameras, tablet computers, smartphones, mobile phones, etc. In CMOS image sensors, photoelectric charges are accumulated in pn junction capacitance of photodiodes (PDs) that serve as photoelectric conversion elements; the photoelectric charges thus accumulated are read out through MOS transistors.
In solid-state imaging devices, micro-miniaturization of pixel sizes is being promoted in accordance with an increase in the number of pixels. Micro-miniaturization is accompanied by a shrink of PD area and a decrease in an amount of entering light, causing lower sensitivity. To compensate the lower sensitivity, white pixels have come into use instead of color filters. The white pixels include clear layers that have little absorption in visible light region. Various proposals have been made concerning materials and methods of fabrication of the clear layers. For example, Patent Literature 1 provides description that the clear layers are made of the same material as that of an interlayer insulating film as an interlayer, e.g., a SiO2 film.